Tests & Diagnosis

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How is Prader-Willi syndrome diagnosed?

There are clinical diagnostic criteria for Prader-Willi syndrome (PWS) that were developed in the past that continue to be useful; however, the current mainstay of a diagnosis of PWS is DNA methylation testing when PWS is suspected. This type of testing can detect abnormal, parent-specific imprinting on the region of chromosome 15 that is responsible for PWS. It determines whether the region is maternally inherited only (i.e., the paternally contributed region is absent) and detects more than 99% of affected people. DNA methylation testing is especially important in those who have non-classic features or are too young to show enough features to make the diagnosis based on signs and symptoms alone.[1]